1. Field of the Invention
The present invention relates to an apparatus for and methods of forming structures on glass or plastic fibers, and more particularly to forming lenses on optical fibers.
2. Description of the Related Art
When coupling optical fibers with other optical fibers or light-producing or light-responsive elements, it is customary to provide lenses for, for example, refracting light carried by the fiber into a larger parallel beam (when the end of the fiber is emitting light) and for refracting a relatively large beam of light into a beam which is sufficiently small to be carried by the fiber (when the end of the fiber is receiving light). These lenses increase the effective area of transmission or reception of the optical fibers, thereby reducing the ratio between the lateral misalignment and the effective area of transmission or reception, thereby making the fiber's connection less sensitive to lateral misalignment.
Additionally, lenses are preferably used on optical fibers for focusing light on surfaces, such as optical disks, and for receiving light reflected from a source, such as an optical disk. The lenses are used to provide the sharp focus necessary to accurately impinge on the track of an optical disk and to collect the scattered or reflected light from the disk surface.
Various means have been used or proposed to couple lenses to the optical fibers, generally involving complicated support structures, special materials, precision finishing, or additional processing steps, which often result in insertion losses and added costs. For example, in U.S. Pat. No. 4,290,667, the optical fiber is glued to a structure which comprises a lens. In U.S. Pat. No. 4,159,863, a well is formed in an end of an optical fiber, then a lens is formed in the well or is glued or otherwise bonded to the fiber.
U.S. Pat. Nos. 4,191,447 and 4,427,879 disclose methods of forming integral lenses on optical fibers by the simple heating of an end of the optical fiber. Heat is applied to the fiber end by flames, soldering irons, or other means and a simple meniscus or spherical shape is obtained. However, there is no way to carefully control the shape of the resulting fiber end, so that low quality lenses may be formed because of localized heating, contaminants, imperfections, gravity and other factors. The shape of the lenses formed by these methods is thus limited and cannot be used in critical or special applications without a high amount of waste or further processing.